JP2542825B2 - Video signal playback device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a video signal reproducing device, and more particularly to a video signal reproducing device having so-called still image reproducing and frame-advancing reproducing functions.

[Prior Art] Conventionally, a video tape recorder (VTR) has a so-called still image reproduction by stopping the tape (hereinafter referred to as still reproduction) and a so-called frame advance reproduction function by conveying the tape by a predetermined amount. Things are being carried out. In the conventional still playback and still image playback in frame advance playback, the tape that is the recording medium is stopped and the rotary head continuously traces the same track of the stopped tape. I was playing still images.

However, in the above-mentioned method, the image is slightly blurred or slightly blurred because the signal is unstable even if a superior composite head is used or the head arrangement is suitable for still image reproduction. In addition, when the frame is fed, there is a drawback that detection of the tape stop position, sudden rise of the motor, and control of the motor such as the brake are considerably complicated.

In addition, in recent years, still reproduction has been proposed and implemented by using a field memory, storing a video signal for one screen in the field memory, and reading it out repeatedly. The still reproduction using this field memory is During normal reproduction, the video signal for one field in the reproduced video signal is converted into a digital signal, stored in the memory, and repeatedly output, so that exactly the same signal is continuously output. As a result, we were able to achieve still image playback without screen blur and noise.

[Problems to be Solved by the Invention] In the still reproduction using the field memory as described above, when switching from still reproduction to normal reproduction, the head is not just tracked by the tape during the period required for the capstan motor to rise. Therefore, the reproduced image deteriorates during that period. Further, since the frame feeding to the field is not properly performed, the reproduced images are discontinuous. Therefore, there is a problem that so-called frame-by-frame reproduction cannot be performed well.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a video signal reproducing apparatus capable of performing beautiful still reproduction without noise using a memory capable of storing one screen.

[Means for Solving the Problems] In the present invention, there is provided a device for reproducing a video signal from a large number of diagonal tracks formed in parallel on a tape-shaped recording medium, and a conveying means for conveying the tape-shaped recording medium. Reproducing means for reproducing the video signal by tracing the tape-shaped recording medium with a rotary head, tracking control means for correcting tracking deviation between the track and the rotary head, and one screen of the reproduced video signal. And a normal reproduction mode for repeatedly writing and reading the video signal reproduced from the tape-shaped recording medium conveyed by the conveying means to the memory, and writing the reproduced video signal to the memory. The video signal is repeatedly read from the memory after being prohibited, and the tape-shaped recording medium is predetermined A mode switching means for switching the mode between a plurality of modes including a still image reproduction mode in which the image is rewound and then stopped.
The mode switching means conveys the tape-shaped recording medium by the conveying means while prohibiting the writing of the reproduced video signal to the memory for a predetermined period according to the normal reproduction command in the still image reproduction mode, and performs the tracking control. The tracking control is performed by the means, and then the normal reproduction mode is switched to.

[Operation] With the above-described configuration, the desired screen in the reproduced video signal is written to the memory and displayed on the screen by the still image reproduction instruction, and at the same time, the tape-shaped recording medium is rewound by a predetermined amount and stopped. After receiving the normal reproduction instruction, tracking control is performed to switch to normal reproduction.

Therefore, a sufficiently good reproduced video signal can be obtained before switching to normal reproduction, and a noise-free image can be obtained even after switching.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a video signal reproducing apparatus according to the present invention. In FIG. 1, HA and HB are rotary heads which rotate with a phase difference of 180 ° and trace alternately on the magnetic tape as well known, and 1, 5 are low-pass filters (LPF) 2 are analog / digital (A / D) converter, 3 is a field memory, 4 is a digital-analog (D / A) converter, 6 is a sync signal separation circuit, 7 is a write clock generation circuit, 8 is an address control circuit, and 9 is a reference clock generation circuit. , 10 and 11 are an instruction unit, 12 is a timing pulse generator, 13 is a reference pilot signal generation circuit, 14 is a tracking error signal (hereinafter referred to as ATF signal) generator (hereinafter referred to as ATF circuit), 15 is an ATF signal zero cross counter,
16 is a capstan motor control circuit, 17 is a capstan motor, 18 is a 30 PG generator that generates a 30 Nz signal (hereinafter referred to as 30 PG) synchronized with the rotation of the rotary heads HA and HB, 19 is a phase synchronization circuit, 20 is 30 PG A counter 21 for counting rising and falling edges of the drum motor, 21 is a drum motor, and SW is a head changeover switch.

The video signal reproduced by the rotary heads HA and HB is switched to S
It is made a continuous signal at W, band-limited by LPF1, and further digitized by the A / D converter 2 at a sampling frequency of 4 f _SC (where f _SC is the chrominance subcarrier frequency of the chroma signal) and the number of quantization bits is 8 bits. After that, the data is written in the field memory 3 in synchronization with the sync signal from the sync signal separation circuit 6 by the write clock of the frequency 4f _SC formed by the write clock generation circuit 7. The reading from the memory 3 is performed by the reference clock of the frequency 4f _SC generated by the reference clock generating circuit 9, and the digital signal read after the correction of the time axis is performed.
It is converted into an analog signal by the D / A converter 4 and output through the LPF 5. The write / read address of the field memory 3 is determined by the address control circuit 8.

Next, the operation of the apparatus shown in FIG. 1 during still reproduction will be described with reference to FIG.

FIG. 2 is a timing chart of the signal waveform in each part of FIG. 1 at the time of still reproduction. FIG. 2 (a) shows a waveform of 30PG, and FIG. 2 (b) shows a well-known four-frequency system in the recording area on the tape. The frequency of the pilot signal recorded by being superposed on the video signal by the above, the figure (c) is the frequency of the reference pilot signal generated by the reference pilot signal generator 13 of the figure (b), and the figure (d) is the still picture. A signal for instructing reproduction, (e) in the figure is a write control signal of the memory 3 which is supplied to the address control circuit 8 when an instruction for still reproduction is made, and (f) in the figure controls the rotation of the capstan motor 17. It is a signal.

Now, when still reproduction is instructed by the instruction unit 10 in FIG. _{1 at} the timing of t ₁ , the signal instructing still reproduction becomes high level as shown in FIG. 2 (d). When the field being reproduced at that time (the field on which the pilot signal of frequency f ₁ is superimposed in the example of FIG. 2) is completely reproduced, the timing pulse generator 12 writes as shown in FIG. 2 (e). A prohibition signal is sent to the address control circuit 8 to prohibit rewriting of the field memory 3. Further, at the same timing as the above timing, as shown in FIG. 2 (f), the capstan motor control circuit 16 generates a reverse drive signal for the capstan motor 17 to rotate the capstan motor 17 in the reverse direction.

Further, at the same time as the above timing, switching of the frequency of the reference pilot signal generated from the reference pilot signal generating circuit 13 is stopped as shown in FIG. 2 (c). As is well known, in the 4-frequency system, 1 in 4 tracks determined by the reference pilot signal
Since the ATF signal is obtained by comparing the pilot signals from both adjacent tracks of one control target track,
While the capstan motor 17 is rotating in the reverse direction, a waviness occurs in the ATF signal in four track cycles. The capstan motor 17 is stopped when the counter 15 calculates the number of undulation zero-cross points by a certain value. As a result, the tape can be stopped when the tape is rewound by a predetermined amount.

Next, the operation during frame advance reproduction will be described with reference to FIG.

FIG. 3 is a timing chart of signal waveforms in each part of FIG. 1 when a frame-advance reproduction instruction is given.
The figure (a) is a waveform of 30 PG, the figure (b) is the frequency of the pilot signal recorded on the track traced by the rotary head by being superposed on the video signal, and the figure (c) is the frame advance reproduction instruction. (D) is a signal for controlling the rotation of the capstan motor, and (e) is a write control signal for the field memory 3 supplied to the address control circuit 8 when a frame advance instruction is issued. FIG. 6F shows the frequency of the reference pilot signal generated by the reference pilot signal generating circuit 13 in FIG.

When the instruction unit 11 shown in FIG. 1 gives an instruction for frame-advance reproduction at the timing of t ₂ , the instruction unit 11 generates an instruction signal as shown in FIG. 3C, and as a result, as shown in FIG. 3D. A control signal is generated from the capstan motor control circuit 16 to rotate the capstan motor 17 in the normal reproduction direction at the same speed as during recording, and at the same time, stop switching the frequency of the reference pilot signal. As a result, the ATF signal is also supplied to the capstan control signal 16, and the capstan motor 17 is rotated while performing tracking control.
Also, set the counter 20 at the same time as the above timing,
Start counting rising and falling of 30PG. At the same time when the count reaches a predetermined number, the field memory write control signal is inverted and supplied to the address control circuit 8 as shown in FIG. 2 (e), and the video signal write to the field memory 3 is started.

At this time, in order to prevent the screen from being disturbed when the video signal read from the field memory 3 and the reproduced video signal from the tape are switched, the phase synchronization circuit 19 compares the phases of the reference clock generation circuit 9 and 30PG. Then head
The rotation of HA and HB is synchronized with the reference clock.

If the instruction unit 11 gives an instruction to perform normal reproduction, the writing is continuously performed after the video signal is written in the field memory 3 again, and the normal reproduction is performed.

On the other hand, when the writing to the field memory 3 is restarted by the frame advance command as described above, this writing is prohibited after a predetermined period (two fields in FIG. 3), and Performs the same operation. That is, the tape is rewound by a predetermined amount, and the tape stands by for the next frame feed reproduction command or the normal reproduction command. By repeating such operations, so-called frame advance reproduction can be realized.

When the number of zero crosses of the ATF signal counted by the counter 15 before the capstan motor is stopped at the time of rewinding the tape is set to n, the frame feed reproduction command causes the writing to the memory to be restarted. Counted by counter 20
The number of rising and falling edges of 30PG is set to about 4 (n + 1). It should be noted that the value of n may be appropriately set according to the rising time of the capstan motor 17 and the like.

Further, the method of determining the tape rewinding amount and the timing of resuming writing to the memory is not limited to the above-mentioned method, but can be determined by counting the control pulse recorded at the tape end. .

[Effects of the Invention] As described above, according to the video signal reproducing apparatus of the present invention, the video signal written in the memory is always a good video signal, so that normal reproduction, still reproduction, and still reproduction to normal reproduction are performed. A good image can be obtained at any of the switching times.

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of a reproducing apparatus as an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of each part of FIG. 1 in response to a still reproduction command, and FIG. 3 is a frame advance command. 3 is a timing chart showing the operation of each part of FIG. In the figure. 1,5: LPF, 2: A / D converter 3: Field memory, 4: D / A converter 6: Synchronous signal separation circuit 7: Write clock generation circuit 8: Address control circuit 9: Reference clock generation circuit 10 , 11: Indication part 12: Timing pulse generator 13: Reference pilot signal generation circuit 14: ATF circuit, 15: Counter 16: Capstan motor control circuit 17: Capstan motor 18:30 PG generator, 19: Phase synchronization circuit 20 : Counter, 21: Drum motor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Sato, 770, Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (56) References JP 61-141280 (JP, A) JP 61- 142882 (JP, A) JP 62-239776 (JP, A) JP 62-163483 (JP, A)

Claims (1)

(57) [Claims] 1. An apparatus for reproducing a video signal from a plurality of oblique tracks formed in parallel on a tape-shaped recording medium, comprising a conveying means for conveying the tape-shaped recording medium, and a tape-shaped recording medium by a rotary head. Reproducing means for tracing the video signal and reproducing the video signal; tracking control means for correcting a tracking deviation between the track and the rotary head; a memory capable of storing one screen of the reproduced video signal; The normal reproduction mode in which the video signal reproduced from the tape-shaped recording medium carried by the device is repeatedly written and read into the memory, and the reproduction video signal is prohibited from being written in the memory and the video signal is repeated from the memory. Still image playback that reads and stops the tape-shaped recording medium after rewinding it by a specified amount Mode switching means for switching the mode between a plurality of modes including a mode, and the mode switching means, in response to a normal reproduction command in the still image reproduction mode, reproduces the reproduced video signal to the memory for a predetermined period. A video signal reproducing apparatus, wherein the tape-shaped recording medium is conveyed by the conveying means while writing is prohibited, and tracking control is performed by the tracking control means, and then the normal reproduction mode is switched.